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MUGA (Multigated) study is a procedure in which patients RBCs are radiolabeled, ECG gated and then ECG gated scintigraphy is obtained. Single or multiple studies of the left or right ventricle are done. Alternative names for the study are RNV (Radio Nuclide Ventriculography) and RNA (Radio Nuclide Angiography).
Data are collected from several hundred cardiac cycles to generate images of the beating heart that is presented as single or composite cardiac cycle.
This study is used to assess the following:
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Regional and global wall motions
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LEFT or RIGHT ventricular ejection fractions
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Cardiac chamber size and morphology
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Ventricular systolic and diastolic function
MUGA may be done in a resting state, during exercise or during pharmacological interventions. Some centers perform a post NTG / sorbitrate MUGA immediately after the exercise MUGA.
Procedure:
1. Patient preparation:
REST:
No special preparations are required at rest. Fasting is preferred. No need to withhold any medications. ECG electrodes must be secured firmly to the skin to ensure optimal ECG tracings.
EXERCISE:
Patient should be fasting at least for 2-4 hours and hemodynamically & clinically stable. Exercise in the form of supine or upright ergometry is generally preferred. Patients who cannot exercise can undergo a pharmacological stress test with dobutamine. Any medication that may interfere pharmacological stress test should be stopped in consultation with treating physician for 24-48 hours prior to the test. All emergency resuscitation measures should be available when conducting such a test. A trained physician for any resuscitation must be available in case of emergency.
INFORMATION PERTINENT TO PERFORMING THE STUDY:
Adequate history should be taken regarding arrhythmias, drugs, cardiac risk factors etc. Evaluation for physical capability should be done. Standard 12 lead ECG should be viewed before the study.
PRECAUTIONS:
1. You should know the safe handling of blood products.
2. When in-vitro labeling is done you should be absolutely certain about administering the blood to the same patient.
3. Patients with unstable heart rhythms or implanted devices should be very closely monitored because heart rate response to exercise is unpredictable in such patients.
RADIOPHARMACUETICALS:
Administered adult dose is usually 15-30mci 99mTc using in-vivo, invitro or modified in vivo methods.
Child dose: 0.2-0.4mci/ Kg body weight. Minimum dose 2- 4 mCi
Largest radiation absorbed dose is to the heart. 0.02mSv / Mbq.
Approximately 25% of the administered dose is excreted by urine within 24 hours.
Stannous pyrophosphate is typically used in most centers.
Stannous DTPA may also be used.
Labeling is least consistent with in-vivo method, intermediate with modified in vivo and best in in-vitro method.
Most of centers prefer in vivo labeling as it is simple & there is no risk of handling blood products.
IMAGE ACQUISITION:
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